Here, \(v\left(T\right)\)  denotes the temperature-dependent Higgs vacuum expectation value, \(\left<\Phi ^\dagger \Phi \right> = v^2\left(T\right)/2\)  during the EWPT, which has been studied in a numerical lattice simulation in Ref. [1]}.
A simple fit formula describing these numerical lattice results, valid at \(130\,\textrm {GeV} \lesssim T \lesssim 160\,\textrm {GeV}\) , has been worked out in Ref. [2]},
\(v\left(T\right) \approx 0.23\,T \sqrt{162 - \frac{T}{1\,\textrm {GeV}}} \,.\) 
